Joint trajectory and power optimization for UAV redeployment against an eavesdropper under fairness constraint

Abstract

This paper focuses on enhancing physical layer security in a UAV-enabled wireless network where a UAV is mounted with a base station. We consider a scenario where a UAV, hovering and serving multi-users, detects an eavesdropper and moves to optimal hovering position. We aim to enhance security while maintaining fairness for the whole service. To achieve this, we not only need to find optimal location considering fairness before and after detecting Eve, but also need to keep fairness during movement. Thus, a new objective is proposed to maintain fair service when moving. Here, we handle three optimization problems: UAV’s optimal hovering point without Eve, optimal hovering point upon detection of Eve, and UAV trajectory while jointly optimizing power allocation. To handle the non-convexity of the formulated problems, we propose a block coordinate descent (BCD) and successive convex approximation (SCA)based algorithm. Simulation results show that our approach achieves superior performance over the existing method in the aspect of various fairness assessments, stability and Quality of Service (QoS) for all users, demonstrating that our design is more practically useful than the conventional ones. Additionally, we utilized the energy model of the rotary wing UAV, which is demonstrated to achieve $34%$ energy efficiency on our system.